1. Field of the Invention
This invention relates to an austenitic stainless steel, more particularly to a low nickel containing chromium-nickel-manganese-copper austenitic stainless steel.
2. Description of the Related Art
U.S. Pat. No. 5,286,310 discloses a low nickel containing chromium-nickel-manganese-copper austenitic stainless steel that has a reduced nickel content and acceptable metallographic structure, mechanical strength, corrosion resistance and workability. The aforesaid austenitic stainless steel contains at least 16.5% by weight of chromium so as to provide acceptable corrosion resistance. However, the chromium content should not exceed 17.5% by weight so as to prevent undesired formation of delta ferrite (δ-ferrite) during hot working and impairment to hot workability. The aforesaid austenitic stainless steel further contains at least 2.5% by weight of nickel so as to improve cold workability and so as to inhibit transformation of austenite into martensite. However, nickel content should not exceed 5% by weight due to the relatively high price thereof.
Although the aforesaid austenitic stainless steel is capable of providing acceptable corrosion resistance and cold or hot workability, the chromium content thereof is still high (previous investigation has shown that at least 17% by weight of chromium is necessary to provide minimum levels of corrosion resistance), which can impair stability of the austenitic stainless steel and which can cause cracking during hot rolling.
The disclosure of U.S. Pat. No. 5,286,310 is incorporated herein by reference.
U.S. Pat. No. 3,615,365 discloses an austenitic stainless steel consisting essentially of up to 0.12% carbon, from about 5 to 8.5% manganese, up to about 2% silicon, from about 15 to about 17.5% chromium, from about 3.5 to about 6.5% nickel, from about 0.75 to about 2.5% copper, up to about 0.05% nitrogen, and the remainder essentially iron with incidental impurities.